1. Field of the Invention
The present invention relates to a buckle apparatus for use in a seatbelt system designed to protect an occupant of a vehicle when an emergency situation occurs, the buckle apparatus being used when the occupant fastens an occupant restraining webbing around his body.
2. Description of the Prior Art
A seatbelt system of the above-described type is arranged such that an occupant engages a tongue plate, which is provided at one end of a webbing, with a buckle apparatus, thereby fastening the webbing around his body.
Such buckle apparatus generally includes a buckle body which is formed by bending a metallic plate material into a U-like shape. The tongue plate is inserted into the buckle body, and a lock plate which is disposed within the buckle body is engaged with the tongue plate, thereby preventing the tongue plate from being pulled out of the buckle body.
Accordingly, it is necessary for the buckle apparatus of this structure to employ a buckle body with a relatively large wall thickness, which fact disadvantageously involves an increase in the weight of the buckle apparatus. Further, the structure of this type of buckle apparatus allows only a single tongue plate to be engaged therewith. It is therefore inconveniently difficult for such a structure to be applied to a buckle apparatus which is required to have two tongue plates engaged therewith at the same time, such as that which is employed in a four-point webbing fastening type seatbelt system, a seatbelt system for restraining a child passenger, etc.